Thousands of microRNAs (21-23 nt ssRNAs) have been identified in animals in the past years [1,2]. Subsequent research on miRNAs has focused on their biochemical processing and mechanism of action [3], the scope of their regulatory programs and their differential expression profiles in development and disease [4]. Furthermore, various si/miRNA constructs are widely used in functional genomics, miRNA cellular/tissue profiles are measured in medical diagnostics [5], and si/miRNAs (and their inhibitors) are in clinical trials for use as medical therapeutics [6, 7].